Experimental assessment of borehole wall drilling damage in basaltic rocks

Technical Report · Sun Jun 01 00:00:00 EDT 1986

OSTI ID:5658923

Fuenkajorn, K; Daemen, J J.K.

Ring tension tests, permeability tests, and microscopic fracture studies have been performed to investigate the borehole damage induced at low confining pressure by three drilling techniques (diamond, percussion and rotary). Specimens are drilled with three hole sizes (38, 76, and 102 mm diameter) in Pomona basalt and Grande basaltic andesite. The damaged zone is characterized in terms of fractures and fracture patterns around the hole, and in terms of tensile strength reduction of the rock around the holes. Experimental results show that the thickness of the damaged zone around the hole ranges from 0.0 to 1.7 mm. A larger drill bit induces more wall damage than does a smaller one. Different drilling techniques show different damage characteristics (intensity and distribution). Damage characteristics are governed not only by drilling parameters (bit size, weight on bit, rotational speed, diamond radius, and energy), but also by properties of the rock. The weaker rock tends to show more intense damage than does the stronger one. Cracks within grains or cleavage fractures are predominant in slightly coarser grained rock (larger than 0.5 mm grain size) while intergranular cracks are predominant in very fine grained rock (smaller than 0.01 mm grain size). The damaged zones play no significant role in the flow path around a borehole plug.

• Research Organization: Arizona Univ., Tucson (USA). Dept. of Mining and Geological Engineering
• OSTI ID: 5658923
• Report Number(s): NUREG/CR-4641; ON: TI86901531
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
ANDESITES
ROCK DRILLING
BASALT
FRACTURES
PERMEABILITY
ROCK MECHANICS
TENSILE PROPERTIES
BOREHOLES
CEMENTS
CLOSURES
EXPERIMENTAL DATA
FORMATION DAMAGE
BUILDING MATERIALS
CAVITIES
DATA
DRILLING
FAILURES
IGNEOUS ROCKS
INFORMATION
MATERIALS
MECHANICAL PROPERTIES
MECHANICS
NUMERICAL DATA
ROCKS
VOLCANIC ROCKS
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